Catherine Quinn
Freelance journalist and feature writer

Hold your shooters, when it comes to tequila there's a new sheriff in town. If you're a regular on the London bar scene, you've probably encountered the Mexican spirit in late-night shots, or margaritas. Not only is the real thing is a great deal more sophisticated, but a new standard – ultra premium – has been added to the annals of quality tequila categorisation.

For the most part the tequila you find in London bars is 'mixto' tequila. This means that the expensive blue-agave which gives high-quality tequila its unique flavour has been adulterated with cheaper foodstuffs like corn, and small amounts of colour and flavouring.

Next up the list is 'sipping' tequila – a substantially higher quality product made of 100% blue agave. Over the past few years we've begun to see this tequila make its way into high-end bars, as bartenders become increasingly aware of the potential of this subtle and complex spirit. Within the 'sipping category' tequila comes unaged (although sometimes rested) 'blanco', or silver tequila, then 'reposado', or 'rested' tequila. This is a legal category defined by the Mexican government, which means the drink must have spent at least two months rested in wooden barrels or tanks. Finally 'anejo' is also legally defined as having being aged for more than a year.

Until recently, 'sipping' and 'premium' were the top categories to which a tequila could aspire. But as producers become ever more innovative with the sheer decadence in which they afford to their production processes, 'ultra premium' has now been brought in to recognise the crème de la crème of tequilas.

Currently in this category you're most likely to see Patron's 'Platinum' or 'Burdeos, and Partida's 'Elegente' on the shelves of style-bars. The former brand has enjoyed magnificent success as America's premium tequila, and has forged a path for other producers. "Patron has really done us a favour" says Brian Van Flandern, Global Brand Ambassador of Don Julio. "They've educated the US in quality tequilas and opened the way for smaller quality producers in America and hopefully the rest of the world."

In the UK, younger US brand Partida has also gained great acclaim for its dedication to food and tequila matching, whilst Jose Cuervo, already well-known on the UK bar scene, is in the process of bringing it's ultra-premium Platina to UK shores. Don Julio, in contrast, is Mexico's favourite premium tequila, and is also edging its way into quality UK retailers, with their Blanco, Anejo and Resposado, and an ultra-premium Real scheduled for arrival anytime soon.

When you reach this level of sophistication, tequila can readily rival spirits like cognac in terms of complexity of flavour, and the smoothness of sipping. Unsurprisingly, achieving a product of this quality involves some highly complex production processes as well. Just as the finest Champagnes require endless care and attention from plantation to harvesting techniques, so premium tequilas call upon an involved process to ensure the best materials go into a bottle.

"The blue agave is actually a desert succulent and is part of the lily family, rather than a cactus" explains Brand Director Chris Spake of Patron. "The tequila process really starts with the terroir, or the soil. The soil in which we grow our agave is a deep red, very rich in iron and other minerals, and we mature our agave for a minimum of seven years in this soil to develop the right sugars." This is in contrast to lower quality tequilas where the agave is force-grown to early maturity.

Where the agave come from is also important. Like the terroir of France, Mexico has varied soil and climate in which to grow agave. Broadly speaking these are split into plantations from high up on the hills and those in the valleys. Where the agave is sourced is a matter of taste rather than superiority. It's generally accepted that tequila made from valley-grown agave is more vegetal and aggressive in flavour, whilst those made from highland plants is softer and more fruity. Premium tequila is made from both, and which is best is a matter of preference – although the larger sweeter plants of the Jalisco highlands seem the favourite of most premiums. But sourcing from a sole area is of primary important.

"There's a lot of agave grown throughout Mexico, and many tequilas use agave from a number of different plantations" explains Henry Bessant, Brand Ambassador for Partida. "Naturally this makes it almost impossible to control the consistency of the finished product without resorting to artificial measures like colouring and added sugar." In contrast the super-premiums all source from a single plantation, or have their own agave estate, allowing them to make the manufacture of their tequilas a far more exacting process.

Once the carefully chosen plantation has been harvested, the mature agave are shaved into a beach-ball sized 'pina', ready for roasting. And even at this stage, the premium manufacturers do everything by hand, shaving down further to the sweet white core than other producers. "We cut into quarters and then very slowly roast the agave over 72 hours" says Brian Van Flandern of Don Julio. "If you imagine a tomato source which has been cooked for a few hours with butter and herbs it will taste pretty good, but slowly simmer it over a few days, and you won't need to add anything to it – it will have a natural sweetness."

So before these high-end tequilas even get to the distillation process, their key ingredient has been coaxed and cosseted through the cutting and roasting. "When you're making high-quality tequila, everything with the agave is done slowly and gently" explains Henry Bessant.

Next comes the distillation. Most tequilas are made in a continuous still; an invention best known for allowing large quantities of gin to be manufactured cheaply in the 1800s. In contrast the ultra-premiums are distilled in a copper pot still – the same used in quality whisky production. Several, such as Patron use their own patented still designs, which are a fiercely guarded secret, and only the choicest cut of the distil taken.

"We only use the hearts of the distillation process" says Mark Barratt, of Cuervo, referring to the tendency of quality producers to dispense with the initial 'heads' and the residual 'tails' of the distillation process. "This makes for much more waste, but it's a far higher quality product."

The results are then double or triple distilled, but despite all this care and attention, the manufacturing process is nowhere near over. Next the tequila is aged, imparting even more complexity to the minutely produced spirit. Depending on the premium, the time aging can vary, but is usually up to three years. "People dismiss tequila because it's only aged for three years" says Brian Van Flandern "But the agave can be grown in the field for up to fifteen years to reach maturity, whereas grain for whiskey or grapes for cognac grow annually."

Choice of barrel is also a hot issue among producers. Patron's latest ultra-premium Burdeos is first aged in American oak whiskey wines barrels, before being distilled a further time, and racked in wine barrels of prestigious French Bordeaux producers, lending the final product an entirely distinct depth of flavour. Whilst the other ultra-premiums carefully source from American and Canadian whisky distilleries.

So with all these sumptuous new tequilas on the market, how should they be drunk? Almost all the producers agree that their ultra-premiums make a superb digestif, taking the place of cognac. The exception is Cuervo, who see their product as a fine-sipper, but also as a potential mixer in ultra-premium cocktails. "I could imagine it making the ultimate margarita combined with other premium products" says Mark Barratt.

In generally, however, the ultra premiums are to be enjoyed solo, and make a great end to a fine meal. "With the Don Julio Real you have flavours of butterscotch, pistachio, caramel, crème brulee – I even get rum raisin ice cream" says Brian Van Flandern. I've worked with cognac before I came to tequila and I have no hesitation in saying that it rivals some of the finest cognacs in the world. Because of the high acid nature of the spirit it works perfectly as a digestif."

With its extra depth of Bordeaux-barrel flavour, Patron's Burdeos is also perfectly positioned as an after-dinner spirit, with notes of vanilla, dried fruit, and raisins.

But slightly before the end of a meal can also work for these tequilas, according to Partida, who have put a lot of energy into food and tequila matching. "It works incredibly with sweet things like desserts" says Henry Bessant.of Partida's Elegente. "Flavours like chocolate it also works very well with. Because it's so complex it also tends to pick out flavour notes of fruits like pineapple, as well as spice flavours."

These ultra-smooth 'sippers' also make a good accompaniment to food with robust flavours such as tapas, grilled fish and meats, and of course, Mexican flavours. In fact several London restaurants such as Green and Red and Wahaca make a dedicated effort to educate their customers into the delights of sipping tequila with their meal.

"It's great with meals with plenty of chilli and lime, which of course, is classic Mexican." says Mark Selby of Wahaca. "Although it's sometimes difficult to persuade customers to sip rather than shoot. We've actually sourced specific hand blown glasses with very heavy bases to deter them!"

So one thing's for certain, whilst premium and ultra-premium tequilas might be making their way into a style-bar near you, they won't be served with salt and lemon. Salud!